[Android] Sort custom search engines based on last visited time and display only top 3 most recentl…

chrome/browser/search_engines/template_url_service_android.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/search_engines/template_url_service_android.h"
 
 #include <stddef.h>
 
 #include "base/android/jni_string.h"
 #include "base/bind.h"
@@ skipping 134 matching lines @@
   template_urls_ = template_url_service_->GetTemplateURLs();
   TemplateURL* default_search_provider =
       template_url_service_->GetDefaultSearchProvider();
 
   auto comp = [&](const TemplateURL* lhs, const TemplateURL* rhs) {
     bool rhs_prepopulated =
         template_url_service_->IsPrepopulatedOrCreatedByPolicy(rhs);
     if (template_url_service_->IsPrepopulatedOrCreatedByPolicy(lhs)) {
       return !rhs_prepopulated ||
              (lhs->prepopulate_id() < rhs->prepopulate_id());
+    } else if (lhs == default_search_provider) {
+      return !rhs_prepopulated;
     }
-    return (lhs == default_search_provider && !rhs_prepopulated);
+    return rhs != default_search_provider && !rhs_prepopulated &&
+        lhs->last_visited().ToTimeT() > rhs->last_visited().ToTimeT();
   };
   std::sort(template_urls_.begin(), template_urls_.end(), comp);

[Peter Kasting, 2016/12/06 06:24:55]

The sort comparator is getting complicated.

I wonder if it would be better to use a couple of calls to std::partition() to
do this.  This would avoid the need to count the elements in the "recently
visited" list at all, since you would be able to compute the size of that
partition directly.  You would still need a sort() call for the first partition
in this case.

Or maybe a sort() with "prepopulated before non-prepopulated, sorted by ID",
followed by a partition() call.

[ltian, 2016/12/07 00:56:43]

Done.

+  int num_remove = CountRemovedSearchEngineNum();
+  template_urls_.erase(template_urls_.end()-num_remove,
+                       template_urls_.end());

[Peter Kasting, 2016/12/06 06:24:55]

Nit: Use resize()

[ltian, 2016/12/07 00:56:43]

Done.

+
+}
+
+int TemplateUrlServiceAndroid::CountRemovedSearchEngineNum() {
+  int num_custom_engine = 0;
+  for (std::vector<TemplateURL*>::const_iterator i = template_urls_.begin();
+      i != template_urls_.end(); i++) {
+    template_url_service_->ShowInDefaultList(*i) ? num_custom_engine :
+        num_custom_engine++;
+  }

[Peter Kasting, 2016/12/06 06:24:55]

Nit: Use std::count_if

[ltian, 2016/12/07 00:56:43]

Done.

+  return num_custom_engine > 5 ? num_custom_engine - 5 : 0;

[Peter Kasting, 2016/12/06 06:24:55]

Nit: Use std::max

[ltian, 2016/12/07 00:56:43]

Done.

 }
 
 void TemplateUrlServiceAndroid::OnTemplateURLServiceChanged() {
   JNIEnv* env = base::android::AttachCurrentThread();
   if (weak_java_obj_.get(env).is_null())
     return;
   LoadTemplateURLs();
 
   Java_TemplateUrlService_onTemplateURLServiceChanged(env,
                                                       weak_java_obj_.get(env));
@@ skipping 118 matching lines @@
 static jlong Init(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   TemplateUrlServiceAndroid* template_url_service_android =
       new TemplateUrlServiceAndroid(env, obj);
   return reinterpret_cast<intptr_t>(template_url_service_android);
 }
 
 // static
 bool TemplateUrlServiceAndroid::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }